20 Fire fighting systems
20.4 Functional requirements .1 General
Fixed fire fighting systems shall be installed in areas representing a major fire risk, and particularly cover equipment containing significant quantities of hydrocarbons.
20.4.2 Firewater (FW) supply system
The FW supply shall be sufficient to cover area with the largest FW demand plus the adjacent fire area with largest demand. The FW demand shall include supply to two hydrants.
The FW ring main shall be dimensioned for the demand of the largest fire area with one segment of the ring main closed and for any FW pump configuration running, and for the demand of both the largest fire area and the largest neighbouring area without any segments closed.
The FW ring main shall be water filled and pressurised in the standby mode. The pressure source shall have the capacity of flow through frost protection bleed lines plus two hydrant hoses.
Firewater ring main sectioning valves shall be easily accessible, car sealed and clearly marked.
If needed the FW ring main shall be equipped with two points (minimum 6 in) for connection to external water supply for commissioning. SOLAS international shore couplings should be used.
The magnitude and effects of pressure surges shall be minimised. Measures such as water filled FW pump risers, air relief valve and vacuum breakers shall be considered.
Screen at seawater inlet and strainer shall be installed. The inlet arrangement shall be designed to ensure that the FW pumps also can function at 150 % of rated capacity.
Normally a system to inhibit marine growth is required, e.g. by injection of hypochlorite.
The system design shall comply with the field specific frost protection requirements, i.e. minimum water flow and/or heat tracing.
Carbon steel and galvanised steel shall not be used in the FW ring main system. For material selection, see OLF Guideline No. 075.
For general piping requirements, see NORSOK P-001 and NORSOK L-002.
The water supply system and level control arrangement in water filled structures shall meet the required reliability.
20.4.3 Firewater pump arrangement
The FW pump system configuration shall at least be equal to 4 x 50 % of the largest fire area with respect to capacity and availability. Alternatively a 3 x 100 % pump system configuration is acceptable.
A procedure shall be prepared defining compensating measures to accommodate temporary reduced FW capacity. The compensating measures shall be defined as part of the design basis.
The FW pump system should include spare capacity for future expansions.
Firewater pump systems shall be self-contained. It shall be possible to start the FW system even if no other systems on the platform are operational.
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The basis for prime mover and FW pump system design shall be NFPA 20.
There shall be a starting sequence logic for the start-up of the FW pumps in accordance with NFPA 20.
Duration of each start attempt does not have to comply with NFPA 20. This includes
• individual FW pump engine sequence logic (repetitive start attempts),
• start of duty pumps on single low gas detection when used for explosion mitigation,
• start of duty pumps on fire detection, see Table 3,
• start of FW pump upon loss of ring main system pressure. There shall be a minimum of two pressure transmitters in the FW ring main providing the low-pressure start signal to the FW pump system. The transmitters shall be located in different segments of the ring main,
• manual start of FW pumps from CCR and FW pump room.
Manual stop of the FW pump engines shall only be possible local to the engines. If flooding of e.g. buoyancy volumes on floating installations or shafts on fixed installations, is a hazard other means for stopping the engines may be evaluated.
Each FW pump engine shall have a starting system with sufficient reliability to satisfy the integrity
requirement for the FW system. Each engine should have two independent starting systems, which do not need to be functionally different. Each system shall have a minimum capacity for six start attempts of minimum 5 s or longer if required by supplier.
Start batteries for the FW pump engines and batteries for the diesel control system shall be located within the same room as the engines. The batteries shall be easily accessible and located above floor level.
A manual isolation switch/valve (car sealed) between the starter motor and the start battery/air bank shall be provided.
The FW pump engine start batteries shall be charged by the FW engine generator while running and in addition charged from main power supply.
Compressed air accumulator capacity and/or battery capacity for FW pump engines shall be in accordance with NFPA 20.
Each FW pump engine shall have its own dedicated day tank sufficient for 18 h continuous full power operation.
The fuel supply line between the FW pump engine and diesel day tank shall be equipped with a valve capable of being closed from outside the FW pump engine room. The valve shall be secured in open position.
The FW pump engine cooling water and/or oil preheat function for diesel engines shall be in accordance with NFPA 20 requirements and supplier’s recommendations.
It shall be possible to operate FW pump engines when ventilation to the room has been shut off.
In case of gas in air inlet to the FW pump engine room, the ventilation to the room shall be stopped and dampers automatically closed and the cooling air shall be taken from the engine room itself. Cooling of the FW pump engine room shall be by an air/FW-cooling unit powered directly from the FW pump engine. The combustion air inlet shall be separated from the ventilation air inlet of the room.
The combustion air inlet shall be equipped with a damper initiated by overspeed. Automatic stop of FW pump engine driven FW pumps shall only be permitted due to overspeeding. Failure of the overspeed securing device should not cause the FW pump engine to stop. Simple reset of the systems shall be possible.
It shall be evaluated if confirmed gas detection in the combustion air inlet shall inhibit FW pump start.
Consideration shall be made to extreme weather conditions to ensure sufficient pump suction pressure on pump duty point.
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A test valve for the FW pumps shall be installed to enable checking of the FW pump curve up to 150 % of design flow rate. The valve shall be able to regulate from zero flow up to 150 % capacity and shall be of low noise design. It shall be possible to measure capacities and pressures.
20.4.4 Deluge system
NFPA 13, NFPA 15 and NFPA 16 should be used as guideline for design of deluge systems. The deluge system shall provide adequate coverage for the relevant fire and explosion scenarios, with respect to both volume and area coverage, horizontal and vertical surfaces.
A fire area may be covered by several deluge valves. All deluge valves covering a fire area shall be released when fire detected anywhere in the fire area. This applies also for manual release of any deluge valve
covering the fire area.
The FW system shall be designed and calibrated such that deluge nozzles will receive water at design pressure not later than 30 s after a confirmed fire signal has been given.
The minimum required densities of FW shall be
• 10 (l/min)/m2 for process areas and equipment surfaces,
• 20 (l/min)/m2 wellhead (including riser balconies, manifolds located on FPSO turrets etc.).
For other areas the protection should be in accordance with ISO 13702.
Foam supply shall be provided for all areas where hydrocarbon or alcohol pool fires are likely to occur.
Deluge shall be automatically released upon confirmed gas detection in areas where effective for explosion mitigation.
It shall be possible to manually activate deluge valve locally, from CCR and at release stations located along the escape routes outside the fire area itself.
Activation of deluge systems shall trigger alarm in CCR. Pressure transmitters shall be fitted downstream deluge, monitor and sprinkler valves to provide confirmed flow signal to CCR.
Deluge valves should be of a type which regulates the downstream pressure and which is not sensitive to pressure surges in the ring main.
Deluge valve arrangement with interfaces shall be such that it can be function tested (at full capacity, if desirable) without release of water into the fire area, i.e. block valve installed on the downstream side of the deluge valve and provision of separate test line. Isolation valve shall also be included upstream of the deluge valve.
Deluge valves shall be provided with manual bypass including flow restriction (if necessary) to match flow through the valve. The bypass line shall be taken from another section of the ring main ensuring FW supply at all times, including maintenance situations.
Deluge valves shall fail in last position upon loss of signal from F&G logic.
For manned installations resetting of deluge, monitor and sprinkler control valves shall normally only be possible local to the valves.
Deluge nozzles for area coverage on fully open process and drilling areas should be of the high velocity types.
The number of low points shall be minimized. All low points in piping downstream deluge and monitor skids shall be equipped with 3 mm weep holes to prevent pockets of water to be entrained. Alternatively the low points shall be equipped with deluge nozzles or auto drain valves.
The need for strainers in deluge system shall be considered. Deluge nozzles shall be without individual strainer.
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Fixed or oscillating monitors may be used as an alternative to deluge coverage for the turret protection if adequate performance can be achieved.
Carbon steel and galvanised steel shall not be used in the deluge system. For material selection, see OLF Guideline No. 075.
20.4.5 Sprinkler system
The sprinkler system shall provide adequate coverage for the relevant fire scenarios, with respect to area coverage on horizontal and vertical surfaces. NFPA 13 should be used as guideline for design of sprinkler systems.
The delivered flow rate of water shall be
• 10 (l/min)/m2 in utility areas, helicopter hangars,
• 6 (l/min)/m2 in LQ.
For other areas the protection should be in accordance with ISO 13702.
It shall be possible to fully function test the sprinkler system by use of a suitably located test sprinkler and using fresh water. There shall be a test and flush connection at the far end of the piping system and at the sprinkler valve(s). The connections shall be easy accessible from deck level and have a drain box located below the connection.
There shall be a pressure sensor downstream of each sprinkler valve and a flow indicator upstream each area indicating in which area release is taking place. Indication in the CCR shall be provided.
Sprinkler valves shall be provided with full capacity manual by-pass.
Priming of wet pipe sprinkler systems with fresh water should be evaluated.
For fresh water filled wet pipe sprinkler systems, the transition from fresh water feed to normal FW shall be automatic and reliable.
Adequate venting facilities with valves shall be provided for wet pipe sprinklers.
For dry pipe sprinkler systems the sprinkler valve arrangement shall be fitted with an accelerator.
The sprinkler heads should be of the frangible bulb type, set to burst at 68 °C, in general areas. However, a higher temperature limit should be selected for areas where high ambient temperatures might be expected.
Carbon steel and galvanised steel shall not be used in the sprinkler system. For material selection, see OLF Guideline No. 075.
20.4.6 Foam system
The foam system shall provide a quick and reliable supply of foam concentrate with correct concentration.
Centralised foam systems shall have a total foam concentrate capacity sufficient for minimum 30 min simultaneously supply to the largest fire area and the largest neighbouring area requiring foam.
For local foam systems the total foam concentrate capacity in each local holding tank shall be sufficient for 30 min supply to the applicable deluge valve skid.
To avoid foaming draining of the foam concentrate tanks shall not be made to the open deck drain.
A system shall be installed which is capable of providing sufficient foam system standby pressure.
The centralised foam concentrate pump system shall comprise of two pump systems and be powered from dedicated drivers or from the FW diesel drivers. If the pumps are connected to FW diesel generator, it shall also be possible to run the pumps from main power in order to run/test pump without starting the FW diesel generator.
Foam pumps shall be equipped with minimum flow control and pump testing facilities. P i d d b S t d d O l i A S f N i k l i O t i 2 0 1 4 0 5 1 2 r o v e y a n a r n n e o r o a + r z - -In order to print this document from Scribd, you'll
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Foam pumps shall during normal operation be in standby mode and start on foam demand.
When in operation, the foam supply shall have an operation pressure of at least 0,2 MPa (2 bar) above the FW pressure to prevent reverse flow. The pressure in the foam ring main shall be presented in CCR.
Foam injector, ejector or proportioner shall provide a pre-determined foam concentration corresponding to the applied foam concentrate type.
Foam shall be injected downstream deluge and monitor control valves to prevent ingress of foam into the FW ring main system.
Block-valves in the foam supply lines shall generally be secured open, e.g. by car sealing.
For a centralised foam system the foam ring main shall be provided with easy accessible isolation valves.
20.4.7 Manual fire fighting
Manual fire fighting appliances, such as monitors, hydrants, hose reels, dry chemical equipment, dual agent hose reels and mobile and portable extinguishers shall provide a reliable and effective tool for fire fighting by manual intervention.
In order to protect people from electrical hazards, relevant equipment (such as switchboards) with voltage above 230 V shall be disconnected before performing manual fire fighting with water. Dedicated facilities shall be provided for this purpose.
Manual fire fighting equipment shall have adequate frost protection, e.g. by heat tracing and/or drain possibilities as applicable.
It shall be possible to reach any area where a fire may occur on the installation with at least two water jets from monitors or hoses.
The FW supply from the ring main to hose reels and FW hydrants shall be such that not more than 50 % of the FW to water hoses and hydrants for one area is affected if one segment of the FW ring main is
unavailable.
Quick operating isolation valves shall be provided for each hydrant.
When monitors are used instead of deluge systems, the requirements for deluge systems such as water density and functionality shall apply.
Monitors shall have sufficient freedom of travel in the horizontal and the vertical plane. Normally they shall be adjustable through 360° in the horizontal plane and from + 60° to - 40° in the vertical plane.
It shall be possible to lock a monitor in any position.
Monitor nozzles shall be of the constant flow type, i.e. the flow shall be the same at both fog and at jet spray setting. The spray angle shall be easily adjusted when in operation. All monitors, except monitors used instead of deluge, should return to maximum spray angle after use.
Automatic drain facilities shall be provided for each FW monitor.
Monitor valves shall fail in last position upon loss of signal from F&G logic.
20.4.8 Hydrants and hose reels NFPA 14 should be used as guidance.
The maximum reaction force on the hose nozzle where only one person is supposed to operate the hose shall not be more than 250 N.
Hydrants
Hydrants shall be located in weather resistant cabinets fitted with heating units where required. One cabinet shall be provided per hydrant.
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The hydrant cabinet shall contain
• 4 off 1½ in bore hoses of an approved fire-resistant type, 15 m in length with instantaneous connection joints to hydrants and nozzles,
• 2 auto to fog nozzles with pistol grip. Capacity minimum 20 m3 /h with two hoses and a nozzle hooked up,
• 2 sets of connecting key.
All hydrants shall have two outlets fitted with 1½ in quick connections of a standard approved type throughout all areas (NOR No. 1).
Hose reels
Non-collapsible hose reels shall have
• within LQ 25 m of 1 in bore hose, capacity approximately 8 m3 /h,
• within all other areas 25 m of 1 ¼ in bore hose, capacity approximately 15 m3 /h.
20.4.9 Helideck fire fighting system
The helicopter deck shall be equipped with adequate fire protection equipment and with sufficient drainage capacity to enable escape and fire fighting in the event of helideck related fires. This shall be achieved by complying with the following sub-requirements:
• a DIFFS shall be the preferred means of active fire protection and shall comply with:
- the water-foam mix shall be applied with a minimum spray height corresponding to the top of the applicable helicopter bodies in calm conditions. This to ensure a safety margin with respect to safe escape, including windy conditions;
- the water density shall be minimum 10 (l/min)/m2 for the helideck;
- full water and foam supply shall be available within 20 s from time of activation;
- the storage capacity of the foam concentrate holding tanks shall be sufficient for 10 min of full discharge of the DIFFS.
• foam monitors (normally not required when DIFFS is installed) shall, when installed, comply with:
- one monitor to be located at each of the three access ways;
- the foam monitor fire fighting system shall be capable of delivering foam on the helicopter deck
maximum 20 s after activation at a rate of minimum 1 500 l/min per monitor at 0,7 MPa (7 barg) nozzle pressure;
- foam monitors shall always start automatically with water spray in the fog position;
- it shall be possible to start monitors in preset oscillation or fixed position from both local and remote protected position;
- risk assessment justifying the use of monitors as an alternative to DIFFS.
• the equipment shall have adequate frost protection, i.e. by heat tracing and/or drain;
• on NNMI the fire fighting system on helideck shall allow for remote operation and control;
• FW and spilled fuel shall be drained in a safe and controlled manner through a dedicated drain system with sufficient capacity. Special attention to location of drain gullies shall be made to helicopter decks on floating installations;
• two dual agent hose reels (combined water/foam and dry chemical hose reel) shall be provided and have:
- sufficient powder for discharge at a rate of 2 kg/s to 3 kg/s for minimum 100 s;
- sufficient foam for minimum 10 min full discharge.
20.4.10 Extinguishing systems in enclosed compartments
Water mist system is the preferred extinguishing system for enclosed compartments such as:
• FW pump generators room;
• cement unit room;
• emergency generator room;
• turbine hoods;
• diesel engine rooms;
• trafo room for oil filled trafos.
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